Steam generator of the drumless type



O 1963 R. MICHEL ETAL STEAM GENERATOR OF THE DRUMLESS TYPE 3 Sheets-Sheet '1 Filed May 27, 1959 14 a 20 I L21 Oct. 8, 1963 R. MICHEL ETAL 3,106,193

STEAM GENERATOR OF THE DRUMLESS TYPE Filed May 27, 1959 3 Sheets-Sheet 2 Oct. 8, 1963 R. MICHEL ETAL 3,106,193

STEAM GENERATOR OF THE DRUMLESS TYPE Filed May 27, 1959 3 Sheets-$heet 3 Fig.6

United States Patent 3,106,193 STEAM GENERATOR OF THE BRUMLESS TYPE Rupprecht Michel, Erlangen, and Johannes Dutt, Buchenbach, near Erlangen, Germany, as'signors to Siemens- Schuckertwerlre Aktiengesellschaft, Berlin Siemensstadt, Germany, a corporation of Germany Filed May 27, 19555 Ser. No. 816,151 Claims priority, application Germany May 30, 1958 8 Claims. (Cl. 122-235) Our invention relates to a steam generator of the drumless or once-through type in which the preheating and evaporation of the working medium up to approximately 80% of evaporation is effected in parallel tubes without interposition of collector drums.

It is an object of our invention to provide a steam generator of this type which requires no expedients for securing de-watering or de-airing and in which the danger of corrosion due to retained steam bubbles, as may occur in downcomer pipes, is avoided to a great extent.

On the basis of tests and considerations relating to forced-flow or once-through boilers in which the evaporation takes place in a single passage of the medium through parallel tubes without interposed collector drums, it has been found that the stability of continuous operation is often considerably impaired if the commencing evaporation takes place in boiler tubes that continually extend upwardly and downwardly in meander fashion. Such instability has the consequence that the boiler cannot be permitted, without danger, to operate in low-load operation because this may cause individual tubes to become differently heated so that some tubes may assume excessively high temperatures.

On the other hand, there are also difficulties of proper de-aeration during start-up of a boiler if the first-traversed water-conducting heating surfaces have their pipes extend upwardly and downwardly. In such a plant, great variations in flow quantity are to be expected during the first few hours of starting-up operation. These variations fade away only when the air is definitely dissolved in water or is entrained by the flow of the working medium. Furthermore, upward-downward meander tubes are also subject to corrosion by steam cracking in the range of commencing evaporation because the steam bubbles may become retained in the down-tubes when the boiler load is below a certain minimum value.

it is an object of our invention to obviate the abovementioned shortcomings of forced-low steam generators.

More particularly, the invention aims at improving the flow stability in such a generator while avoiding deairing trouble and steam-cracking phenomena due to retainment of steam bubbles.

According to a feature of our invention, we dispose in a single-pass steam generator of the above-described type, the parallel tubes in the evaporation zone, up to approximately 30% steam content, in a horizontal direction or with a continuous upward inclination or in a stepwise upward course so that any downwardly extending lengths of tubes in this evaporation zone are eliminated. Only subsequently thereto, if necessary, can the parallel tubes be mounted to extend upwardly and downwardly in meander shape.

In such a system according to the invention any expedients for eliminating air are unnecessary because in the continuously rising portion of the tubing, traversed by the working medium, this medium is evaporated up to 30% so that the air, corresponding to its partial pressure, admixes itself to the steam and thus is forcefully entrained by the flow of working medium without difficulty during start-up operation. An interior corrosion of the tubes can occur only if the commencement of the initial steam "ice formation takes place in downward tubes. The invention permits avoiding this by a preceding, rising evaporator length of tubing.

When applying the invention to an upright-type of cyclone firing-chamber with burners entering the chamber from above, the tubes can be so designed that the entire group of parallel tubes at first extends upwardly along the outer periphery of the cyclone and only subsequently, namely where a steam content of about 30% can be reliably counted upon, does the group extend from that location and from the neck portion of the cyclone firing-chamber in a downward and subsequently upward direction. -The cooling of the cyclone neck portions can be effected by a multiple number of upward and downward turns of all parallel tubes.

When applying the invention to a frontal firing chamber with dry ash flue, the following tube layout can be provided: First traversed by the working medium are tubes along the firing-chamber funnel, the lateral walls and the rear walls, the tubes being disposed in horizontal meanders sequentially located one above the other. When the working medium leaves these rising meander tubes, its steam content amounts to at least 30%. Thereafter the tubes extend on the burner Wall in the form of meanders extending upwardly and downwardly, the tubes being placed one above the other in order to form recesses for accommodating the burners.

The invention will be further explained with reference to the drawings showing embodiments of steam generators relative to their components essential for the invention but in otherwise simplified and schematic representation.

.FIG. '1 shows in schematic perspective a steam generator according to the invention applied to a cyclone firing system. J

FIG. 2 shows another embodiment of a cyclone-type boiler in schematic and simplified representation.

FIG. 3 is a schematic perspective view of the boilers shown in FIGS. 2 and 4 seen laterally from above.

FIG. 4 shows another modification of a cyclone-type boiler in schematic representation.

FIGS. 5 and 6 are perspective front views and rear views respectively of a boiler system embodying the invention for a frontal type of firing with dry-ash removal.

For lucidity of illustration the boiler tubes are shown in the drawings in such a fashion that the tube sections located closest to the observer are shown by full lines, whereas the sections in the rear of the boiler are indicated by broken lines. I

According to FIG. 1 the firing-chamber of the cyclone is formed by the cylindrical outer wall 1, burners being provided in the upper conical surface or cyclone ceiling 2 in uniform distribution along the periphery. The burners located in the cyclone ceiling are heated in conventional manner with gas, coal-dust or the like fuel. The cyclone bottom is composed of frusto-conical portions 3 and 4. Located in the interior of the cyclone chamber is a cylindrical insert 5 which upwardly merges with a frusto-conical, upwardly widening neck portion '6. The neck portion 6 itself, or an additional transition member on top of the neck portion, maybe so shaped that its circular bottom cross section merges upwardly with a square or rectangular cross section.

The system of parallel tubes enters from below into the firing-chamber funnel, as represented by the arrow 7. Represented schematically by the line 8 is a single tube of the group of parallel tubes. As is symbolically indicated by the line 8, the parallel tubes enter from below at first into the firing-chamber funnel and then distribute themselves uniformly over the entire periphery of the firing-chamber. The tubes 8 rise with a uniform upgrade, from a lining on the cyclone bottom 4 and 3.

'Thereafter the parallel tubes wind themselves helically up to the cylindrical portion 1. Further helical windings of the parallel tubes extend upwardly along the outer surface of the cylindrical cyclone portion 1 of the firingchamber. The tube portion 9 is located on the rear side, the portion It) on the front. The tube section 11 again extends along the rear side and the section 12 is located on the front side of the firing-chamber.

In section 13, the parallel tubes pass between the burners located in the cyclone ceiling 2, whence the tubes'extend in section 14 vertically along the wall of the frustoconical neck 6 up to an upper reversing loop 14a. Up to this reversing loop the entire system of parallel tubes rises continuously. At the point of the loop 14a the medium has attained a vapor content of at least 30%. From the reversing loop 14a, each of the parallel tubes extends downwardly along a section denoted by 15 which forms simultaneously the carrier structure for the interior insert 5. Next following the downwardly extending tube section 15 is an upwardly winding helical portion 16 located at the front, a rear section 17, and a front section 18. These tube sections 16, 1'7 and 18 extend upwardly to a neck pontion 19 where they are followed by upwardly winding helical sections 1? and 2.0. The exit of the parallel tubes is symbolically indicated by an arrow 21.

In the embodiments shown in FIGS. 2, 3 and 4, the same reference numerals are used as in FIG. 1 for respectively similar elements. The distribution of the individual burners 22 around the cyclone ceiling is apparent from FIGS. 2 and 3, the same distribution being applicable in the embodiment of FIG. 1.

in contrast to the course of the parallel tubes shown in FIG. 1, the boiler of FIG. 2 is provided with a system of parallel tubes which, after reaching the cycloneceiling area 2, do not extend to the upper edge of the neck portion 6 but which return vertically downward from a reversing point 14!; near the bottom of the neck portion.

According to FIG. 3 the neck portion 6 is cylindrical rather than conical, and the parallel tubes extend from the burner surface directly to a reversing point Me at the upper rim of the neck 6', whereafter the individual tubes are twice extended downwardly and upwardly as indicated by 15 so as to form a lining for the entire neckinsert 6. This requires an adaptation and coordination of the diameter of the neck-insert 6, the tube length, the tube diameter and cold-water velocity. In this manner, using conventional cyclone dimensions, it is possible to obtain a complete coverage of the neck-insert 6 with, for example, approximately 90 parallel tubes. From neck-insert 6, the system of parallel tubes communicates with a number of exit collectors 23, of which only one is shown in FIG. 2.

In the embodiment of FIG. 4 the above-mentioned cylindrical interior neck-insert is provided with an upwardly widening neck 6. After the parallel tubes are twice wound helically outwardly of and then downwardly along path on the insert 5, they extend subsequently in helical fashion upwardly along the peripheral surface of the mid-portion as shown at 19'. 'The tube system then leads at 21 into the exit collector.

In the steam generator illustrated in FIGS. 5 and 6 the burners protrude into the firing-chambers through respective openings 24-. The entrance point of the system of parallel tubes, symbolically denoted by arrows 25 and 26, are located at the bottom of the front side of the steam generator (\FIG. 5), whereas the tube exits, denoted by arrows 27, 23, are located at the top of the rear wall 33 (FIG. 6). The tube lines with directional arrows shown thereon in FIGS. 5 and 6 represent in each case the outer tubes at the respective right and left boundaries of a multiple strand of parallel tubes, the arrows also indicating the flow direction of the medium passing through the tubes. The water, forced through the system of tubes by a pump (not shown) enters at 25, 2'5 and passes through tubes 31 which are mounted in gradually rising meander bands along the inclined walls of the fire-chamber :funnel 29. Following these firingchamber tubes 31 are groups of meander tubes 32 which extend along the rear wall 33 and the lateral walls 34 and which likewise rise from one meander path to the other. After these tube sections are traversed by the medium, the zone is reached where an evaporation up to approximately 30% stearn content has taken place. The tubes now continue in meander bands 35 located on the front wall side 36 (FIG. 5) leaving sufficient space for the openings 24 to be traversed by the burners. The latter meander bands 35 extend upwardly and downwardly, as shown in FIG. 5, the ultimate portion being followed by a horizontal tube section 37 extending around the lateral walls 34 to the rear wall 33 and from which the working medium emerges at 27 and 28 to pass into the next evaporator and super-heater sections of the forced-flow steam generator.

it should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention as set forth in the appended claims.

We claim:

1. A continuousdlow steam ge-nenator comprising a firing-chamber and having a collector-less preheater and evaporator tube system for preheating and evaporating the working medium up to about to steam content, said tube system forming heating surfaces adjacent to said firing-chamber and comprising a group of parallel tubes having a water-inlet end and an outlet end, said group having a first portion of tubes within which the working medium flows generally upwardly, with the exclusion of downward flow, from said inlet end up to a location in said system where the working medium has attained about 30% evaporation, and means within said tube system for avoiding instabilities in flow of the working medium therethrough comprising downwardly directed tubes located within said firing chamber and within which tubes the working medium flows downwardly, said last named tubes having heating surfaces adjacent said firing chamber and being connected immediately subsequent to said first portion of tubes.

2. A continuous-flow steam generator comprising a firing-ehamber and having a collector-less preheater and evaporator tube system for preheating and evaporating the working medium up to about 80% steam content, said tube system forming heating surfaces adjacent to said filing-chamber and comprising a group of parallel tubes having a water inlet and an outlet end above said inlet, the tubes of said group having an upward gradient at all locations between said inlet and a higher location in said system where the working medium has attained about 30% evaporation, and means within said tube system for avoiding instabilities in flow of the working medium therethrough comprising downwardly directed tubes located Within said firing chamber and within which tubes the working medium flows downwardly, said last named tubes having heating surfaces adjacent said firing chamber and being connected immediately subsequent to said first portion of tubes.

3. A continuous-fiow steam generator comprising a firing-chamber and having a collector-less preheateir md evaporator tube system for preheating and evaporating the working medium up to about 80% steam content, said tube system forming heating surfaces adjacent to said firing-chamber and comprising a group of parallel tubes having a water-inlet end and an outlet end, said group having intermittently positioned tubes exclusively comprising alternate horizontal portions and ascending portions and extending from said inlet end up to a location in said system where the working medium has attained about 30% evaporation, and means within said tube systern for avoiding instabilities in flow of the working medium therethrough comprising downwardly directed tubes located within said firing chamber and within which tubes the working medium fiows downwardly, said last named tubes having heating surfaces adjacent said firing chamber and being connected immediately subsequent to said first portion of tubes.

4. A steam generator according to claim 1, said finingcharnber forming an upright cyclone and having burners inserted into said firing-chamber from above, a neck portion having a cylindrical insert portion extending centrally into said firing-chamber, all tubes of said first portion extending in ascending sense along the outer periphcry of said cyclone firing-chamber, then passing along said neck portion in upward direction, said downwardly directed tubes passing subsequent to said first portion in downward direction along said neck portion.

5. A steam generator according to claim 4, said second portion comprising a multiplicity oi upward and downward turns in said group of parallel tubes located along said neck portion for cooling of the latter, the tubes located on said neck portion being directly connected to the first portion of said tubes on said periphery or said firing chamber.

6. A steam generator according to claim 1 having frontal, lateral and rear walls, said frontal wall having openings therein 'for burners, a funnel-shaped firontal firing-chamber having sloping walls for dry ash removal, said first portion of said group of parallel tubes fiorming horizontally extending meander strands ascendingly mounted one above the other and located on said sloping walls of said firing-chamber and on the lateral walls and the rear wall of said generator for passing the working medium therethrough, said second portion of said group of parallel tubes forming meander tubes connected subsequent t said first portion and extending upwardly and downwardly on said frontal wall and [forming recesses around said openings in said firontal wall for the burners, said first portion extending up to a location in said system where the working medium has attained approximately 3 0% steam content before joining said second portion.

7. A continuousfiow steam generator comprising a firing chamber and having a collector-less preheater and evaporator system up to about 80% to 100% steam content, said tube system forming heating surfaces adjacent to said firing chamber and comprising a group of parallel tubes defining heating surfaces and having an inlet end and an outlet end for the working medium, said group having a first portion of tubes arranged to make the working medium therein fiow exclusively upwardly from said inlet end up to about 30% evaporation, subsequent portions of said group of tubes having heating surfaces adjacent said firing chamber and defining upwardly and downwardly traversed flow paths for said medium, means within said tube system for avoiding instabilities in flow of the working medium therethrough comprising downwardly directed downcomer tubes having heating surfiaces adjacent said firing chamber and connected between said first portions and said subsequent portions of said group.

8. A forced-flow single-pass steam generator, comprising a firing chamber having an intensively heated temperature Zone, and a collector-less prcheater and evaporator tube system- -for preheating and evaporating the working medium up to a steam content of about to said tube system having upwardly and downwardly traversed heating surfaces and including parallel meander tubes mounted within said generator, a first portion of said meander tubes being part of said evaporator tube system and forming an exclusively upward course of flow for the working medium to evaporate and carry the latter only up to a location in said system corresponding to an evaporation of 30% to 50% of the weight of said medium flowing through said first portion, and a second portion of said tubes joined to said first portion and located within said intensively heated temperature zone, said second portion forming downwardly traversed heating surfaces in the range of at least 30% evaporation by weight of the working medium, whereby stability and continuity of the flow of the working medium is increased.

References Cited in the file of this patent UNITED STATES PATENTS 2,526,339 Esnault-Polterie Oct. 17, 1950 2,827,022 Krause et al. Mar. 18, 1955 FOREIGN PATENTS 770,456 Great Britain Mar. 20, 1957 969,986 Germany Aug. 7, 1958 

1. A CONTINUOUS-FLOW STEAM GENERRATOR COMPRISING A FIRING-CHAMBER AND HAVING A COLLECTOR-LESS PREHEATER AND EVAPORATOR TUBE SYSTEM FOR PREHEATING AND EVAPORATING THE WORKING MEDIUM UP TO ABOUT 80% TO 100% STEAM CONTENT, SAID TUBE SYSTEM FORMING HEATING SURFACES ADJACENT TO SAID FIRING-CHAMBER AND COMPRISING A GROUP OF PARALLEL TUBES HAVING A WATER-INLET END AND AN OUTLET END, SAID GROUP HAVING A FIRST PORTION OF TUBES WITHIN WHICH THE WORKING MEDIUM FLOWS GENERALLY UPWARDLY, WITH THE EXCLUSION OF DOWNWARD FLOW, FROM SAID INLET END UP TO A LOCATION IN SAID SYSTEM WHERE THE WORKING MEDIUM HAS ATTAINED ABOUT 30% EVAPORATION, AND MEANS WITHIN SAID TUBE SYSTEM FOR AVOIDING INSTABILITIES IN FLOW OF THE WORKING MEDIUM THERETHROUGH COMPRISING DOWNWARDLY DIRECTED TUBES LOCATED WITHIN SAID FIRING CHAMBER AND WITHIN WHICH TUBES THE WORKING MEDIUM FLOWS DOWNWARDLY, SAID LAST 